Disc libraries, such as optical disc libraries, may be used for archival storage. Discs, such as optical storage discs, are stored within a disc library such that they are accessible by a disc retrieval unit (DRU) able to move single discs between storage locations and drives that read data from and write data to the discs. A disc selector system is needed as part of the DRU to allow single discs to be reliably selected and secured for transport by the DRU without disturbing other discs in the disc library.